1. Field of the Invention
The present invention relates to connectors for electric cords that are suitably used as connectors of extension cords extended from power cords of power tools used mainly outdoors, such as gardening tools including bush cutters and hedge trimmers.
2. Description of the Related Art
In general, a power cord of a gardening tool is designed to have a length (about 30 cm) not to interact with a blade in order to prevent the power cord from being damaged by the blade. Thus, because the power cord is very short, it is necessary to connect an extension cord with the power cord for supplying electric power when the gardening tool is used outdoors. Various improvements have been conventionally made to plugs (hereinafter called “male connectors” on a side of a power cord and connectors (hereinafter called “female connectors”) on a side of an extension cord. For example, in order to improve waterproof performance at a connecting portion between the male and female connectors, a cover portion is provided on the side of the male connector for covering the connecting portion.
Further, a technique has been proposed for preventing the male and female connectors from being easily unplugged, in which a connection fixing member having hooks on opposite sides is attached extending between the power cord and the extension cord, while a string is wound around and between the hook on the male connector side and the hook on the female connector side so that male and female connectors may not be easily disconnected, for example, even in the case that the extension cord has been accidentally stepped on.
However, because this hook-type connection fixing member has a problem in resulting low workability and increase in cost as it cannot be easily attached to the cord and the string cannot be easily wounded. For this reason, there has been proposed a female connector having a lock mechanism. U.S. Pat. No. 7,484,986, Japanese Patent No. 3051768 and Japanese Patent No. 3082680 disclose a technique concerning a female connector with a lock mechanism. According to this lock-type connector, because the connection can be locked by a lock mechanism when a male connector is inserted and connected, the connection condition can be more easily and reliably maintained compared to the above hook-type fixing member. Therefore, it may improve the workability (to enable quick gardening work) and reduce the cost because no any additional members, such as a fixing member, are required.
However, the known female connectors with the conventional lock mechanisms still have various problems. The female connector with the lock mechanism as disclosed above U.S. Pat. No. 7,484,986 cannot be applied to a male connector with a connecting cover portion. Normally, the connecting cover portion on the side of the male connector extends to such a position that the connecting terminals may not be projected outward the connecting cover portion. If the connection cover portion is configured to provide a connecting depth that is too deep compared with the insertion allowance of the female connector, an end portion of the connecting cover portion may interfere with an unlock button of the lock mechanism. As a result, a waterproof function of the connecting cover portion may be impaired or a function of the lock mechanism may be impaired if the unlock button is inadvertently pressed. For these reasons, the known female connector with the lock mechanism is difficult to be applied to an extension cord for connection with a power cord of a gardening tool.
Further, a look mechanism disclosed in Japanese Laid-Open Patent Publication No. 4-292885 (U.S. Pat. No. 3,051,768) requires a lock claw provided to one of male and female connectors and an engaging portion provided to the other of the connectors to be engaged with the lock claw. Therefore, it lacks versatility.
Moreover, a lock mechanism disclosed in Japanese Laid-Open Patent Publication No. 10-92512 (U.S. Pat. No. 3,082,680) is not designed to be used to a male connector with a connecting cover portion and cannot be applied as a connector lock mechanism for an extension cord used for extending a power cord of a gardening tool.
Therefore, there is a need in the art for a connecting device that can ensure performance of functions of a connection cover and a look mechanism.